There exist many devices and methods for controlling fluid flows, whether these flow are in open channels or in closed conduits. Areas in which such devices and methods find use include medical, industrial, automotive, aeronautical, sewage treatment and water management, among many others.
Many of these areas require very precise control of small quantities of fluid. Such areas include medical infusion systems, pharmaceuticals production, various vehicle systems. In many of these areas, complex mechanical or electromechanical solutions exist, although attempts have been made to find electromagnetic solutions.
An indication of the state of the art is provided by U.S. Pat. No. 3,982,722, entitled "Magnetic Control Valve." This patent describes a fluid control valve for a fluid system, particularly an air-conditioning system in a vehicle. A flow passage in the system is defined by a "radially flexible tubular member so that the flow area" thereof is variable. Three electromagnets are arranged coaxially about the tubular member, such that an annular space is formed between the electromagnets and the tubular member. Of the three electromagnets, the internal diameter of the middle one is smaller than the diameter of the outer ones, so as to create a constriction in the annular space. A volume of small iron particles is located in the annular space. In order to constrict the flow area of the tubular member, the middle electromagnet is operated so as to attract the iron particles thereto, such that they accumulate in the central area and apply a radially inward force to the tubular member, thereby narrowing the cross-sectional area thereof. The tubular member is allowed to expand when the extreme electromagnets are operated so as to attract the iron particles away from the center.
Disadvantages of the above-described structure include the fact that it provides throttling only of a fluid flow, and that it is incapable of providing high resolution, real time control of a fluid flow.